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GeezerVison is showing github.com — gh-118234: Avoid socket failure with missing SYSTEMROOT env var on Windows by jhohm · Pull Request #134363 · python/cpython

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@jhohm

@jhohm jhohm commented May 20, 2025 •
edited by bedevere-app Bot
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Resolves #118234 by checking for the SystemRoot environment variable and, if it is missing, setting it based on GetWindowsDirectoryW.

As described in the issue, the default path of the provider DLL is stored in the registry as "%SystemRoot%\System32\mswsock.dll" which does not resolve without SystemRoot set (typically to "C:\Windows").

  • Issue: sockets and asyncio on Windows depend on SYSTEMROOT env var #118234

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jhohm added 3 commits May 20, 2025 12:25
@jhohm
Avoid socket failure with missing SYSTEMROOT env var on Windows
d353545 
Resolves python#118234 by checking for the SystemRoot environment variable
and, if it is missing, setting it based on GetWindowsDirectoryW.

As described in the issue, the default path of the provider DLL is
stored in the registry as "%SystemRoot%\System32\mswsock.dll" which does
not resolve without SystemRoot set (typically to "C:\Windows").
@jhohm
blurb
bf89233
@jhohm
Fix indentation to conform to PEP 7.
674ec21
@bedevere-app bedevere-app Bot mentioned this pull request May 20, 2025
sockets and asyncio on Windows depend on SYSTEMROOT env var #118234
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@bedevere-app bedevere-app Bot added the awaiting review label May 20, 2025
@jhohm
Merge branch 'python:main' into pythongh-118234
76c2645
@vstinner

vstinner commented May 20, 2025

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I don't think that it's a good idea to set SYSTEMROOT environment variable on import socket. It's a surprising side effect. I suspect that other Python stdlib modules don't work well without SYSTEMROOT.

cc @zooba
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@zooba

zooba commented May 20, 2025

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Yeah, I don't love this, and certainly not as part of socketmodule. It might make sense in python.c, to detect whenever someone launches Python with an empty environment, but it's probably even better in subprocess to warn people before they launch with an empty environment.

In my experience, this only ever happens when launching from Python. I've not seen any other language cause it. This list linked in the bug has the main ones, and we should probably just ensure that subprocess always sets them if the caller omits them.
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@jhohm

jhohm commented May 21, 2025

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Sent gh-134435 instead.
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@jhohm jhohm closed this May 21, 2025
@jhohm jhohm mentioned this pull request May 22, 2025
gh-118234: Document Python subprocess requirement on SystemRoot env, add RuntimeWarning #134435
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@jhohm @vstinner @zooba
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